Bebop "message" and "union" definition benchmarks

Hello,

It would be nice to have _Bebop_ **message** and **union** definition(s) benchmarked as well. In practice, I find myself relying on **message** and **union** more often than bare **struct** and I suspect that would be the case for most non-trivial applications as well. Since these are less efficient than **struct**, it would be interesting to see how they fare.